JP6405751B2 - Method for producing fine cellulose - Google Patents

Description

The present invention relates to the production how the fine cellulose to the cellulose as a starting material.

In recent years, against the background of global warming, environmental pollution, waste problems, etc. due to depletion of resources and an increase in the concentration of carbon dioxide in the atmosphere, the amount of fossil resources used at the time of production is low, and disposal is possible with low energy. Furthermore, the use of environmentally friendly materials that emit less carbon dioxide has attracted attention.
In addition, biodegradation represented by materials derived from biomass resources that do not use fossil resources as a raw material but part or all of them as natural raw materials, and polylactic acid that decomposes in the environment into water and carbon dioxide Active use of functional materials is expected.

Among biomass materials, cellulose, which accounts for about half of its production, is expected to be used effectively due to its large production. In particular, it has high strength, high elastic modulus, extremely low coefficient of thermal expansion, and is also expected to have an entanglement effect between fibers. It is expected to be applied as a function-imparting agent, such as being used as an agent. In recent years, development has been vigorously advanced in many institutions.
However, it cannot be said that cellulose is often used as a material for its large production. One reason is the low solubility and dispersibility in aqueous and non-aqueous solvents.

Cellulose is a homopolysaccharide in which D-glucopyranose, which is a 6-membered ring of glucose, is linked by β- (1 → 4) glucoside, and has hydroxyl groups at the C2, C3 and C6 positions. Therefore, a strong hydrogen bond is formed in and between the molecules and does not dissolve in water or general solvents.
One of the most common uses of cellulose by chemical treatment is carboxymethylation. This is because the carboxyl group is randomly introduced into the hydroxyl group at the C2-position, C3-position, and C6-position, and depending on the degree of substitution, a material that is water-soluble and can be used as a thickener is obtained with a high degree of substitution. Insoluble carboxymethylated cellulose fibers and various materials can be obtained.

However, in the carboxymethylation reaction of cellulose, since a large amount of organic solvent is used and toxic monochloroacetic acid is used, there are problems in environmental pollution and waste liquid treatment. Moreover, since the introduced carboxyl group has no distinction in the position of the hydroxyl group, the product has a non-uniform chemical structure. Furthermore, there is a problem that high physical properties such as strength and elastic modulus derived from high crystallinity composed of regular self-assemblies inherent in cellulose are deteriorated due to chemical treatment.
In recent years, a method for treating cellulose using an oxidation reaction using 2,2,6,6-tetramethyl-1-piperidinyloxy radical (TEMPO) as a catalyst has attracted attention. When this method is used, the hydroxyl group at the C6 position of cellulose is selectively oxidized, and a carboxyl group is introduced via an aldehyde group. Furthermore, when the amount of carboxyl groups introduced is adjusted, a transparent dispersion can be obtained by various dispersion treatments in water. In that case, the cellulose is disperse | distributed to the microfibril level, and is disperse | distributing in the nanofiber form within the range of width several to several 200 nm. Also, in this TEMPO oxidation reaction, the organic solvent is not used, and the reaction process is extremely adaptable to the environment, for example, the reaction is completed in a short time under normal conditions of normal temperature and normal pressure. In the TEMPO oxidation reaction, it is possible to use cellulose as a fibrous nanodispersion or a liquid state, and since the load on the environment is low, the treatment and oxides by the TEMPO oxidation reaction are new to cellulose. It is expected as a use form.

On the other hand, attempts have been made for a long time to refine cellulose fibers by mechanical force and utilize microcellulose and suspensions thereof as industrial materials.
For example, Patent Document 1 discloses a technique for treating an aqueous suspension of fibrous cellulose at high pressure and high speed using a high pressure homogenizer or the like.
However, in the technique disclosed in Patent Document 1, since the aqueous suspension of fibrous cellulose is processed only by mechanical processing, the processing unit is likely to be clogged, and the processing efficiency is low. There is a problem of requiring processing times.
In addition, many studies have been made to efficiently perform a finer treatment of cellulose by performing pretreatment such as enzyme treatment, acid chemical treatment, alkaline chemical treatment, and autoclave treatment. For example, Patent Document 2 discloses a technique for decomposing cellulose as a pretreatment for mechanical treatment for enzyme treatment or chemical treatment.

Japanese Examined Patent Publication No. 63-44763 Japanese Patent Laid-Open No. 6-10288

However, in the techniques described in Patent Documents 1 and 2, since a substance that finally becomes an impurity is added to the cellulose raw material, a cleaning process for removing the impurity is necessary, and in this cleaning process, There arises a problem that the yield is inevitably reduced and the outflow of minute pieces is inevitable.
The present invention is intended to solve such problems, and a method for producing microcellulose, microcellulose, and molding using microcellulose to promote industrial use of natural resources and to expand use applications. The purpose is to provide a body.

In order to achieve the above object, one embodiment of the present invention includes a decomposition step of decomposing a cellulosic material starting from cellulose in a dry process,
A micronization step of micronizing the cellulosic material with a machine,
The decomposition step is a step that does not include a cleaning step using a liquid,
A method for producing fine cellulose, comprising producing fine cellulose having an average fiber length in a range of 5 μm to 30 μm and an average fiber diameter in a range of 0.2 μm to 0.8 μm.

One embodiment of the present invention is a decomposition step of decomposing a cellulosic material starting from cellulose in a dry manner;
A micronization step of micronizing the cellulosic material with a machine,
In the micronization step, in addition to the cellulosic material to be micronized contains only a dispersion medium,
A method for producing fine cellulose, comprising producing fine cellulose having an average fiber length in a range of 5 μm to 30 μm and an average fiber diameter in a range of 0.2 μm to 0.8 μm.

Another embodiment of the present invention is a method for producing fine cellulose, wherein in the decomposition step, a molecular chain of the cellulosic material is cut by irradiating an electron beam or a gamma ray.
Another embodiment of the present invention is a method for producing fine cellulose, wherein the irradiation dose is in a range of 10 kGy to 1000 kGy.

Another embodiment of the present invention is a method for producing fine cellulose, which includes a chemical treatment step of chemically treating the cellulosic material as a pre-step or a post-step of the decomposition step.
Another embodiment of the present invention is the method for producing microcellulose, wherein in the decomposition step, the moisture content of the cellulose-based material is in the range of 5 wt% to 90 wt%.
Another embodiment of the present invention is the method for producing fine cellulose, wherein the fine cellulose has a cellulose I-type crystal system.

Another embodiment of the present invention is a microcellulose manufactured using the above-described microcellulose manufacturing method.
Another embodiment of the present invention is a molded body using the above-described microcellulose as a material.

  According to one aspect of the present invention, a method for producing microcellulose, a microcellulose produced by the method for producing microcellulose, and the microcellulose as materials for promoting industrial use of natural resources and expanding the use applications. It becomes possible to provide the used compact.

It is a figure which shows the manufacturing method of micro cellulose in 1st embodiment of this invention. It is a figure which shows the modification of 1st embodiment of this invention. It is a figure which shows the modification of 1st embodiment of this invention. It is a figure which shows the modification of 1st embodiment of this invention. It is a figure which shows the modification of 1st embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
(Method for producing fine cellulose)
As shown in FIG. 1, the manufacturing method of the micro cellulose of 1st embodiment has a decomposition process (step S10) and a refinement | miniaturization process (step S11), and processes a process in order of a decomposition process and a refinement | miniaturization process. Then, it is a method of adjusting the fine cellulose (step S12).
In the method for producing fine cellulose, cellulose-based materials using cellulose as a starting material include, for example, wood pulp such as mechanical pulp, chemical pulp, and semi-chemical pulp, specifically, bleached and unbleached kraft wood pulp, water It is possible to use decomposed kraft wood pulp, sulfite wood pulp and the like, as well as waste paper, bacterial cellulose, valonia cellulose, squirt cellulose, cotton cellulose, hemp cellulose and mixtures thereof.
In the first embodiment, a case where a cellulose material having a cellulose I type crystal form is used as a suitable cellulose material will be described.

(Disassembly process)
Hereinafter, the decomposition process of a cellulosic material is demonstrated.
In the decomposition of cellulosic materials, enzyme treatment, acid chemical treatment, alkaline chemical treatment, and autoclave treatment have generally been performed. In these decomposition reactions, enzymes and chemicals are processed sequentially from the surface of the material to be decomposed, so the surface area is increased by predispersing the material to be decomposed in advance in order to decompose uniformly and effectively. The method of making it is common.
In this preliminary dispersion stage, a liquid such as water is used as a dispersion medium.
On the other hand, the method for producing fine cellulose according to the first embodiment has a feature that even if the material to be decomposed is a solid having a certain volume, the decomposition treatment is uniformly decomposed over the surface and inside. Therefore, the preliminary dispersion process as described above is not required. Therefore, the decomposition process in the manufacturing method of the micro cellulose of 1st embodiment is implemented in a dry type.

That is, in the first embodiment, a method of treating a cellulosic material without exposing it to a liquid in the decomposition step is used. Furthermore, after that, the washing process using the liquid is not included, and the cellulose-based material that has undergone the decomposition process is transferred to the next process without being exposed to the liquid by using only the cellulose-based material as the material. Can do.
If the cellulosic material decomposition process contains other than cellulosic material, a cleaning process using liquid will be required for the purpose of removing impurities such as enzymes and drugs after the decomposition process, and the manufacturing costs associated with the cleaning In addition, the manufacturing process is increased and the yield is reduced with the outflow of decomposition products in the cleaning process.

Further, when a perishable liquid such as water is used for washing after the decomposition step, deterioration and decay progress is accelerated, so that it is necessary to strictly limit storage conditions. Furthermore, since it is not exposed to the cleaning liquid after the decomposition step, it is possible to easily perform a process that dislikes the cleaning liquid thereafter.
In the manufacturing method of the micro cellulose of 1st embodiment, the manufacturing cost reduction and the freedom degree of design increase significantly by not passing through the washing | cleaning process after a decomposition | disassembly process.

In this way, when the cellulosic material undergoes the decomposition step, it does not contain impurities other than the cellulosic material, so in the subsequent refinement step, it is not necessary to consider the affinity between the dispersion medium and the impurities. There is also an effect of expanding the options.
As a dry decomposition method in the method for producing fine cellulose of the first embodiment, a method of irradiating an electron beam or a gamma ray can be used.

When the cellulosic material is irradiated with an electron beam or gamma ray, there is an effect of promoting the modification or decomposition of the material according to the irradiation dose or the characteristics of the material. Generally, such a modification / decomposition mechanism is caused by generation of radicals by breaking bonds between atoms. In some cases, the molecular chain is cleaved by this radical, and in other cases, the radical is instantaneously recombined to form a new covalent bond. In the case of natural polymers such as cellulose, decomposition proceeds predominately against recombination, so that the effect of reducing the molecular weight can be obtained by cleaving the molecular chain by electron beam irradiation or gamma ray irradiation. It becomes possible.
When a cellulosic material is treated by electron beam irradiation or gamma ray irradiation, the water content of the cellulosic material including water affects the decomposition behavior.

Specifically, water irradiated with electron beams or gamma rays generates radicals, which may accelerate the degradation of cellulosic materials, while the presence of water blocks electron beams and gamma rays. The decomposition efficiency may be reduced. Alternatively, since the molecular chain behavior of the material varies depending on the water-containing state, the frequency of contact between the generated radicals increases or decreases, and the lifetime of the remaining radicals, that is, the duration of the decomposition effect varies.
In the case of the cellulosic material in the present invention, the moisture content is preferably in the range of 5 wt% to 90 wt% in terms of weight fraction. This is because if the water content of the cellulosic material is less than 5 wt%, the cellulosic material is too cohesive and subsequent dispersion treatment becomes difficult, and handling after treatment becomes difficult. On the other hand, when the moisture content of the cellulosic material is larger than 90 wt%, the shielding effect of electron beam irradiation or gamma ray irradiation increases, and the decomposition efficiency of the cellulosic material decreases.

As an electron beam irradiation method, any of a curtain type, a scan type, a plasma discharge type, and the like can be applied.
As the gamma ray, cobalt 60 can be used as a radiation source. The irradiation dose is preferably in the range of 10 kGy or more and 1000 kGy or less. This is because, when the irradiation dose is less than 10 kGy, the decomposition ability is insufficient, and when the irradiation dose is larger than 1000 kGy, only the decomposition efficiency equivalent to 1000 kGy can be obtained and the irradiation energy becomes excessive. It is.

It is preferable that oxygen does not exist as an environment for irradiating electron beams or gamma rays. This is because the presence of oxygen inhibits the formation of covalent bonds, and the oxygen concentration is preferably 500 ppm or less.
Since gamma rays have a very high material transmission capability, the irradiation surface is not particularly limited, and there is no problem from any surface.

Regarding the electron beam, the transmission capability of the substance varies depending on the acceleration voltage. The higher the acceleration voltage, the higher the transmission capability of the electron beam in the substance. In the case of water, the accelerating voltage of the electron beam is 2 MeV and has a transmission capability of about 8 mm. Therefore, it is necessary to consider the surface to be irradiated with an electron beam depending on the form of the material. An acceleration voltage in the range of 0.1 MeV to 10 MeV is applicable. This is because if the acceleration voltage is lower than 0.1 MeV, the electron beam transmission ability is low, and the effect of electron beam irradiation is limited only to the vicinity of the material surface. On the other hand, in an apparatus having an acceleration voltage higher than 10 MeV, the scale of the facility becomes too large to be realistic. Further, in terms of electron beam transmission capability and equipment scale, the acceleration voltage is more preferably in the range of 1 MeV to 5 MeV.
As the form of the cellulosic material when the electron beam or gamma ray is processed, the water contained in the cellulosic material is excessively evaporated during the treatment in a state where the electron beam or gamma ray can decompose the cellulosic material. The case is not limited as long as the packaging material for packaging the cellulosic material does not adversely affect the cellulosic material due to decomposition products generated by electron beam treatment or gamma ray irradiation. For example, a cellulosic material covered with an aluminum foil may be treated with an electron beam or a gamma ray.

(Miniaturization process)
Hereinafter, the step of refining the cellulosic material will be described.
In a cellulosic material, it becomes possible to refine | miniaturize a cellulose material more efficiently by performing a micronization process using a machine after passing through a decomposition | disassembly process. This is because, in the decomposition process, cellulose molecules are partially decomposed and the entanglement between cellulose fibers is loosened, or the molecular chain is cut, so that it is possible to reduce the energy input in the refinement process. Because.

As a dispersion method in the miniaturization step, various known mechanical treatments can be used. For example, homomixer processing, mixer processing with a rotating blade, high pressure homogenizer processing, ultra high pressure homogenizer processing, ultrasonic homogenizer processing, nanogenizer processing, disc type refiner processing, conical type refiner processing, double disc type refiner processing, grinder processing, ball mill processing , Kneading treatment with a biaxial kneader, underwater facing treatment, and the like. Among these, from the viewpoint of miniaturization efficiency, a mixer process with a rotary blade, a high-pressure homogenizer process, an ultra-high pressure homogenizer process, an ultrasonic homogenizer process, and a grinder process are preferable. Of these processes, two or more processing methods can be combined and distributed.
Thus, it is possible to prepare micro cellulose by performing a decomposition process and a refinement | miniaturization process about a cellulosic material.

In addition, as a fiber shape of a micro cellulose, it is preferable that an average fiber length is 30 micrometers or less and an average fiber width is 0.3 micrometer or less. The obtained fine cellulose can improve the uniformity in mixing with other materials as a paste or as a dispersion together with a liquid dispersion medium.
Furthermore, the degree of freedom of design in terms of functionalization and workability is improved, such as forming a thin film by coating using various coating methods. In particular, a coating film made of a cellulose material system having a cellulose I-type crystal system is known to have a high gas barrier property, and a gas barrier is formed on various substrates using the microcellulose dispersion according to the present invention. A layer may be formed.

In addition, the fiber shape of the fine cellulose is such that the dispersion prepared in the range of 0.001 wt% or more and 0.01 wt% or less is spread on a slide glass and dried and observed with an optical microscope, or 0.0001 wt%. The fine cellulose dispersion prepared in the range of 0.001 wt% or less is developed on mica with a smooth surface, dried, observed by SEM, 10 microfibers are randomly extracted, and the average value is calculated. Is required.
In addition, the microcellulose obtained by the manufacturing method of the microcellulose of 1st embodiment or a microcellulose dispersion may contain a metal etc.

Metals include gold, silver, platinum, palladium, ruthenium, iridium, rhodium, osmium, platinum group elements, and metals such as iron, lead, copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum. Alternatively, an alloy thereof, an oxide, a double oxide, a carbide, or the like can be used.
As a method for supporting the metal, in addition to mixing fine particles such as metal or metal oxide, a fine cellulose dispersion having a carboxyl group forms a metal or metal oxide complex, and a reducing agent is added. It can be deposited as metal particles. When this supporting method is used, fine metal particles are uniformly immobilized on the fiber surface of the fine cellulose, and therefore, the effect can be efficiently exhibited by a small amount of metal.

In addition, in the range where aggregation and precipitation are not generated, various additives including water-soluble polysaccharides and various resins may be included for the purpose of increasing the charge repulsion between fibers and controlling the viscosity of the dispersion. . For example, chemically modified cellulose, carrageenan, xanthan gum, guar gum, gum arabic, sodium alginate, agar, solubilized starch, glycerin, sorbitol, antifoaming agent, water-soluble polymer, synthetic polymer and the like can be used. Alternatively, various solvents may be included for imparting functionality such as coatability and wettability. In this case, alcohols, cellosolves, glycols and the like can be used. Furthermore, various dyes, pigments, organic fillers, and inorganic fillers may be included for the purpose of imparting design properties.
Moreover, in order to improve water resistance and electrolyte solution resistance, various crosslinking agents may be included. In this case, for example, oxazoline, divinylsulfone, carbodiimide, dihydrazine, dihydrazide, epichlorohydrin, glyoxal, organic titanium compound, organic zirconium compound, and the like can be used. Moreover, it is possible to adjust pH by adding an acid or an alkali for the purpose of improving the reactivity.

  The above-described first embodiment is an example of the present invention, and the present invention is not limited to the above-described first embodiment, and the present invention may be applied to other forms than this embodiment. Various modifications can be made according to the design or the like as long as they do not depart from the technical idea. Furthermore, the above-described first embodiment includes inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some structural requirements are deleted from all the structural requirements shown in the first embodiment described above, the problem described in the column of the problem to be solved by the invention can be solved, and is described in the effect of the invention. In the case where the effect obtained is obtained, a configuration from which this configuration requirement is deleted can be extracted as an invention.

(Effects of the first embodiment)
If it is the manufacturing method of the micro cellulose of 1st embodiment, it will become possible to promote industrial utilization of a natural resource, and to expand a utilization use. In addition to this, it is possible to provide a microcellulose produced by a method for producing microcellulose for promoting industrial use of natural resources and expanding the usage, and a molded body using the microcellulose as a material.
Specifically, it is possible to obtain fine cellulose that can be used for various purposes at a high concentration without complicated operations. In particular, since only the cellulose-based material that is the raw material for the fine cellulose in the decomposition step is included, there is no need for a cleaning step for removing impurities such as enzymes and drugs, which is indispensable in conventional methods for decomposing cellulose. In addition to this, it is possible to perform processing while maintaining a high solid content of cellulose, and furthermore, since there is no concern about a decrease in yield in the cleaning process, productivity and practicality can be improved.

(Modification)
Hereinafter, modifications of the first embodiment will be described.
(1) In 1st embodiment, although the manufacturing method of micro cellulose was made into the method which has a decomposition | disassembly process and a refinement | miniaturization process, it is not limited to this, As shown in FIG. 2, manufacture of micro cellulose In addition to the decomposition process (step S20) and the miniaturization process (step S21), the method may include a chemical treatment process (step S22) as a subsequent process of the decomposition process. In FIG. 2, the process of finally adjusting the fine cellulose is indicated as “Step S23”.
The chemical treatment step is a step for the purpose of imparting functionality to the micro cellulose and simplifying the fine treatment.
When the chemical treatment step is a subsequent step of the decomposition step, radicals and reaction terminals generated in the decomposition step can be eliminated by chemical treatment, and the chemical stability of the material can be improved. Furthermore, it becomes possible to perform the process of the refinement | miniaturization process which becomes a post process of a chemical treatment process with low energy.

(2) In the first embodiment, the method for producing microcellulose is a method having a decomposition step and a micronization step, but is not limited to this, and as shown in FIG. In addition to the decomposition process (step S31) and the miniaturization process (step S32), the method may include a chemical treatment process (step S30) as a pre-process of the decomposition process. In FIG. 3, the process of finally adjusting the fine cellulose is indicated as “Step S33”.
When the chemical treatment step is a pre-step of the decomposition step, since the cellulosic material retains a strong fiber shape, the yield is unlikely to deteriorate even after the treatment and the washing efficiency is improved. Furthermore, when a by-product is generated in the decomposition step, it is possible to suppress the production of the by-product by performing chemical treatment in advance.

(3) In 1st embodiment, although the manufacturing method of micro cellulose was made into the method which has a decomposition process and a refinement | miniaturization process, it is not limited to this, As shown in FIG. 4, manufacture of micro cellulose In addition to the decomposition process (step S41) and the miniaturization process (step S43), the method has a chemical treatment process (step S40) as a pre-process of the decomposition process, and further a bleaching process (step S42) as a post-process of the decomposition process. ). In FIG. 4, the process of finally adjusting the fine cellulose is indicated as “Step S44”.
A bleaching process is a process which prevents coloring of a cellulosic material. The cause of coloring of the cellulose-based material may be an aldehyde or a double bond contained in the produced cellulose due to a side reaction due to the influence of electron beam, gamma ray, heat or the like.

As the bleaching method, an existing method can be used. For example, chlorine treatment, hypochlorite treatment, chlorine dioxide treatment, oxygen treatment, hydrogen peroxide treatment, ozone treatment, etc. can be used. . Moreover, you may use the method which combined these 2 or more types. Alternatively, a method for preventing coloring by oxidizing or reducing aldehyde in cellulose is also useful.
The oxidation method and the reduction method are not particularly limited and are appropriately selected depending on the purpose. As the oxidation method, for example, a method of treating with sodium chlorite under acidic conditions can be used. In addition, as a reduction method, for example, a treatment method using the reducing power of sodium borohydride can be used. Moreover, you may use combining these oxidation and reduction | restoration, hydrogen peroxide treatment, etc.

  In addition, as shown in FIG. 5, you may implement a bleaching process by including in other processes, such as setting it as the process (micronization / bleaching process) performed in the middle of a micronization process. In FIG. 5, the chemical treatment process is indicated as “Step S50”, the decomposition process is indicated as “Step S51”, the refinement / bleaching process is indicated as “Step S52”, and finally, the micro cellulose. The process of adjusting is indicated as “Step S53”.

Examples of the present invention will be described below. The following examples are examples of the present invention, and the present invention is not limited to these examples.
(Invention Example 1)
In Inventive Example 1, microcellulose was prepared by the following procedure.
(1) Reagents / Materials Cellulose: Bleached Kraft Pulp (Fletcher Challenge Canada “Machenzie”)

(2) Decomposition process The above bleached kraft pulp was used as the cellulosic material. At this time, the moisture content of the bleached kraft pulp was 7 wt%. Using an area type electron beam irradiation apparatus Curetron (manufactured by Nissin High Voltage), an electron beam with an irradiation dose of 100 kGy was irradiated at an oxygen concentration of 200 ppm and an acceleration voltage of 2 MeV. The electron beam irradiation dose was calculated to be 96.5 kGy from the difference in absorbance before and after irradiation with the dosimeter.
(3) Refinement process Furthermore, the cellulose which decomposed | disassembled at the decomposition | disassembly process was added to water as a dispersion medium, and it processed for 1 hour using the mixer (Osaka Chemical, absolute mill, 14,000 rpm). A fine cellulose dispersion having a solid content concentration of 1% was obtained.

(Invention Example 2)
In Invention Example 2, a fine cellulose dispersion was prepared under the same conditions as in Invention Example 1, except that the irradiation dose of the electron beam was changed by 300 kGy in the decomposition step.
(Invention Example 3)
In Invention Example 3, a microcellulose dispersion was prepared under the same conditions as in Invention Example 1 except that, in the decomposition step, gamma rays with an irradiation dose of 100 kGy were used instead of electron beam treatment.

(Comparative Example 1)
In Comparative Example 1, a fine cellulose dispersion was prepared under the same conditions as in Invention Example 1 except that the decomposition step was not performed.
(Comparative Example 2)
In Comparative Example 2, a fine cellulose dispersion was prepared under the same conditions as in Example 1 except that water was added to the bleached kraft pulp in the decomposition step and the water content was 95 wt%.

[Evaluation]
The fiber shape of the fine cellulose dispersions obtained in Invention Examples 1 to 3 and Comparative Examples 1 and 2 was measured as follows.
[Fiber shape]
The fine cellulose dispersion after the refining treatment was hydrated to adjust to 0.001 wt%, developed on a slide glass and naturally dried overnight, and observed with an SEM. Furthermore, the fiber length and the fiber width were measured for each of arbitrary 10 fibers, and the average value was obtained.

  As shown in Table 1, by subjecting bleached kraft pulp as a cellulosic material to decomposition treatment by irradiation with electron beam or gamma ray, and then subjecting it to refinement treatment, the present invention example has finer fibers than the comparative example. It was confirmed that it was possible to prepare a dispersion of fine cellulose having a shape.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the method for promoting industrial use of a natural resource and expanding a utilization use. According to the method for producing fine cellulose of the present invention, it is possible to obtain fine cellulose that can be used for various purposes at a high concentration without complicated operations. In particular, it does not require a step of removing impurities such as enzymes and drugs, which is indispensable in the conventional method for decomposing cellulose, and furthermore, it can be processed while maintaining a high solid content of cellulose. Since there is no concern that the yield is lowered when recovering from the reaction medium after decomposition, the productivity is high and practical. In addition, the fine cellulose dispersion prepared by the method for producing fine cellulose of the present invention has excellent uniformity in mixing with various additives, resins, metal particles, etc., and molding including coating materials. It can be used as a body material.

  S10, S20, S31, S41, S51 ... decomposition step, S11, S22, S32, S43 ... refinement step, S12, S23, S33, S44, S53 ... step for finally adjusting microcellulose, S21, S30, S40 , S50 ... chemical treatment step, S42 ... bleaching step, S52 ... miniaturization / bleaching step

Claims (6)

A decomposing step of decomposing cellulosic material starting from cellulose in a dry manner;
A micronization step of micronizing the cellulosic material with a machine,
The decomposition step is a step that does not include a cleaning step using a liquid,
In the decomposition step, the molecular chain of the cellulosic material is cut by irradiating an electron beam with an environment having an oxygen concentration of 500 ppm or less and an accelerating voltage within a range of 0.1 MeV to 10 MeV.
A method for producing fine cellulose, comprising producing fine cellulose having an average fiber length in a range of 5 µm to 30 µm and an average fiber diameter in a range of 0.2 µm to 0.8 µm. A decomposing step of decomposing cellulosic material starting from cellulose in a dry manner;
A micronization step of micronizing the cellulosic material with a machine,
In the decomposition step, the molecular chain of the cellulosic material is cut by irradiating an electron beam with an environment having an oxygen concentration of 500 ppm or less and an accelerating voltage within a range of 0.1 MeV to 10 MeV.
In the micronization step, in addition to the cellulosic material to be micronized contains only a dispersion medium,
A method for producing fine cellulose, comprising producing fine cellulose having an average fiber length in a range of 5 µm to 30 µm and an average fiber diameter in a range of 0.2 µm to 0.8 µm. The method for producing fine cellulose according to claim 1 or 2, wherein the irradiation dose of the electron beam is in the range of 10 kGy or more and 1000 kGy or less . The method for producing microcellulose according to any one of claims 1 to 3 , further comprising a chemical treatment step of chemically treating the cellulosic material as a pre-step or a post-step of the decomposition step. . The method for producing microcellulose according to any one of claims 1 to 4 , wherein in the decomposition step, the water content of the cellulosic material is in the range of 5 wt% to 90 wt%. . The said micro cellulose has a cellulose I type crystal system, The manufacturing method of the micro cellulose described in any one of Claims 1-5 characterized by the above-mentioned.

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